The Ganga is the most sacred river in the sub-continent, and revered by millions.It is also among the top ten rivers at risk. The key threat to the river is indiscriminate abstraction of water from the river, leavng it unable to maintain its ecological integrity or to satisfy the needs of riparian communities. In 2008, WWF, in association with various partners, embarked on an exercise to assess the environmental flow requirements of the Ganga, using the Building Block Methodology as part of its Living Ganga Programme. This method takes into accounts various ecological and human needs of the river. This article presents the report brought out by WWF on 'Assessing flow requirements for the Upper Ganga'